A fluid flow process, or flow process, typically includes any process that involves the flow of a fluid through pipes, ducts, or other conduits, as well as through fluid control devices such as pumps, valves, orifices, heat exchangers, and the like. Flow processes are found in many different types of industries such as the oil and gas industry, refining, food and beverage industry, chemical and petrochemical industry, pulp and paper industry, power generation, pharmaceutical industry, and water and wastewater treatment industry. Additionally, the flow process may involve many different types of fluids, such as single phase fluids (e.g., gas, liquid or liquid/liquid mixture) and/or multi-phase mixtures (e.g. paper and pulp slurries or other solid/liquid mixtures), wherein the multi-phase mixture may be a two-phase liquid/gas mixture, a solid/gas mixture or a solid/liquid mixture, gas entrained liquid or a three-phase mixture. Currently, a variety of sensing technologies exist for measuring various physical parameters of the fluids in an industrial flow process, wherein the physical parameters may include, for example, volumetric flow rate, composition, consistency, density, and mass flow rate.
One such sensing technology is described in commonly-owned U.S. Pat. No. 6,609,069 to Gysling, entitled “Method and Apparatus for Determining the Flow Velocity Within a Pipe” (hereinafter “'069 patent”), which is incorporated herein by reference in its entirety. The '069 patent describes a method and corresponding apparatus for measuring the flow velocity of a fluid flowing within an elongated body, such as a pipe, by sensing vortical disturbances convecting with the fluid. The method as disclosed in the '069 patent includes providing an array of at least two sensors disposed at predetermined locations along the elongated body, wherein each sensor is for sampling the pressure of the fluid at the position of the sensor at a predetermined sampling rate. The method also includes accumulating the sampled data from each sensor at each of a number of instants of time spanning a predetermined sampling duration and constructing from the accumulated sampled data at least a portion of a so called k-ω plot, where the k-ω plot is indicative of a dispersion relation for the propagation of acoustic pressures emanating from the vortical disturbances. Furthermore, the method includes identifying a convective ridge in the k-ω plot, determining the orientation of the convective ridge in the k-ω plot and determining the flow velocity based on a predetermined correlation of the flow velocity with the slope of the convective ridge of the k-ω plot.
Another such sensing technology is described in commonly-owned U.S. Pat. No. 6,354,147 (hereinafter “'147 patent”) and U.S. Pat. No. 6,732,575 (hereinafter “'575 patent”) to Gysling et. al, both of which are incorporated by reference herein in their entireties. Both the '167 patent and the '575 patent describe a spatial array of acoustic pressure sensors placed at predetermined axial locations along a pipe. The pressure sensors provide acoustic pressure signals to signal processing logic which determines the speed of sound of the fluid (or mixture) in the pipe using any of a number of acoustic spatial array signal processing techniques with the direction of propagation of the acoustic signals along the longitudinal axis of the pipe. The speed of sound is provided to logic, which calculates the percent composition of the mixture, e.g., water fraction, or any other parameter of the mixture, or fluid, that is related to the sound speed, wherein the logic may also determine the Mach number of the fluid.